The invention concerns an electric motor having a stationary annular stator with wound stator poles and a rotatably mounted rotor having annularly distributed permanent magnets or electromagnets of alternate polarity. The invention further concerns a cable drive having a driven cable guide pulley.
Electric motors have hitherto already been used in cableway drives, in particular in regard to lift systems (cableway systems with people transport). Hitherto the failure of the electric motor involved the necessity of switching over to an emergency drive which for example was diesel-driven in order to be able to evacuate the cableway system. During those change-over procedures which generally take up a great deal of time, the passengers had to wait in the cablecars or cabins or on the chairs, which in winter can result in the passengers suffering from hypothermia.
An object of the invention is to provide an electric motor which in particular is suitable for cableway drives, which is highly reliable in operation and which therefore entails a high level of availability.
In accordance with the invention, in an electric motor of the general kind set forth in the opening part of this specification, that is achieved in that the stator is composed of a plurality of separate stator segments with their own, preferably three-phase current connections, wherein each stator segment is fed by way of the respective current connections from its own frequency converter.
In that respect it is advantageous if each stator segment is of a multi-pole configuration, wherein the winding lines are taken in series or parallel over at least two poles. In that way it is possible to provide a structure in which each stator segment forms the stator of its own, preferably permanently excited synchronous machine which in principle is capable of running on its own.
In that way it can be provided that, in the event of failure of one or more stator segments (for example due to a winding short-circuit or failures in the associated frequency converter) the electric motor can continue to run generally, without additional measures. The situation then only involves a reduction in the power or torque of the overall electric motor to the stator segments which are then in operation. In practice between three and ten and preferably between four and six such stator segments will be provided.
By way of a relay or contactor in the feed lines between the frequency converter and the stator segment, it is possible to protect the respective frequency converter of a failed stator segment from damaging feedback effects. An electronic monitoring system which for example monitors the current to the individual stator segments can detect the failure of stator segments and indicate same to the operator for example on a display panel.
The structure according to the invention of the stator made up of a plurality of stator segments with their own current connections, in the case of an electric motor with a stationary annular stator having wound stator poles and a rotatably supported rotor, makes it possible for same to be constructed even with relatively large dimensions (for example diameters of two or more meters) and also on geographically difficult routes if the stator segments are each in the form of respective separate modular structural units which are releasably secured independently of each other to a stator carrier. Those structural units can then be easily transported for example by means of a helicopter to the mountain top station of a cableway system and assembled on site to form a stator of the electric motor. Even in the event of failure of such a stator segment unit, it can be easily and simply replaced. That means that stockkeeping is also reduced.
As already mentioned the electric motor according to the invention is suitable in particular for cableway drives, in which respect it is possible for the cable guide pulley itself or a part which is non-rotatably connected thereto to be in the form of the rotor of the electric motor. It is however also possible for the electric motor to be connected to the cable guide pulley in per se known manner by way of a transmission.
Further advantages and details of the invention are described in greater detail with reference to the specific description.